(a) Field of the Invention
The present invention relates to a thin film transistor array panel, and in particular, to a thin film transistor array panel used as a panel for a liquid crystal display.
(b) Description of the Related Art
A typical liquid crystal display (“LCD”), which is one of widely used flat panel displays, includes two panels having a plurality of electrodes generating electric field, a liquid crystal layer interposed therebetween, and two polarizers attached to outer surfaces of the panels for polarizing light The LCD applies voltages to the electrodes to reorient liquid crystal molecules in the liquid crystal layer, thereby adjusting the amount of light passing therethrough. The LCD uses one of the characteristics that voltage application varies orientations of the liquid crystal molecules, and the LCD employing transmittance or reflection of light requires an internal or external light source since the liquid crystal is not self-emissive.
A thin film transistor array (“TFT”) panel for an LCD is used as a circuit board for driving pixels in an independent manner. The TFT array panel includes a scanning signal wire or a gate wire for transmitting scanning signals, an image signal wire or a data wire for transmitting image signals, a plurality of TFTs connected to the gate and the data wire, and a plurality of pixel electrodes connected to the wires through the TFTs for displaying images.
The pixel electrodes are designed to overlap the gate wire and the data wire for securing aperture ratio of the pixels, and a thick insulating layer having a low dielectric constant is provided between the pixel electrodes and the gate wire and the data wire in order to minimize parasitic capacitance generated therebetween.
However, there is a problem that undesired inversion of the arrangement of the liquid crystal molecules occurs around contact holes of an insulating layer for connecting the pixel electrodes and the data wire, and this causes light leakage to show disclination, thereby degrading display quality. The reason is that the direction of the electric field generated by the pixel electrodes formed along slopes of the insulating layer is opposite the orientations of the liquid crystal molecules, and thus the arrangement of the liquid crystal molecules is broken. Although the light leakage is blocked by designing opaque films such as the gate wire and the data wire to be wide, this reduces the aperture ratio, particularly for a high-resolution LCD.